The invention relates to an electrical machine having a permanent-magnet-excited rotor, and more particularly, a rotor of an electrical machine having several plate-like or lamellar permanent magnets arranged on its perimeter for each rotor pole at a point directly at the air gap adjacent to the stator of the machine.
An electrical machine having a permanent-magnet-excited rotor is described in German Patent No. U-80 18 686. Due to production engineering and cost considerations, the permanent magnets used for these types of rotors are designed as flat, rectilinear plates or strips. In the case of one rotor, if several permanent magnets are configured side-by-side on the rotor perimeter for each rotor pole, then irregularities in the magnetic field of the individual rotor poles result because of the finite gaps between the individual, adjoining magnets. These irregularities cause harmonic fields, which when combined with stator winding and stator slotting fields, can produce oscillating torques.
It would be advantageous to provide an electrical machine having a permanent-magnet-excited rotor designed to avoid oscillating torques caused by the interaction of stator and rotor harmonic fields.